Optical disc, optical disc drive, optical disc recording/ reproducing method, and integrated circuit

ABSTRACT

A big pattern for a run-in area which allows data reproduction to be performed stably even when the recording density of an optical disc is increased is provided. An optical disc according to the present invention includes tracks, each of which divided into a plurality of recording blocks. Each of the plurality of blocks includes a run-in area and a data area. In the run-in area, a prescribed run-in bit pattern is recordable; and in the data area, bit patterns having a plurality of bit lengths obtained by modulating data as a recording target in accordance with a prescribed modulation rule are recordable. In this optical disc, at least one of spatial frequencies corresponding to the bit patterns having the plurality of bit lengths is higher than a cutoff frequency. The run-in bit pattern recordable in the run-in area includes the bit patterns having the plurality of bit lengths, from which the bit pattern corresponding to the frequency higher than the OTF cutoff frequency has been excluded.

This application is a continuation of U.S. patent application Ser. No.12/273,674 filed on Nov. 19, 2008, which claims priority to JapaneseApplication Nos. 2007-300135 filed on Nov. 20, 2007, 2008-175423 filedon Jul. 4, 2008, and 2008-290292 filed on Nov. 12, 2008, and is herebyincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a recording format usable for recordinginformation on an information recording medium, and a technology forrecording or reproducing information in accordance with the recordingformat.

2. Description of the Related Art

Recently, research and development of high density optical discs hasbeen actively conducted. Currently, for example, Blu-ray Disc (BD) hasbeen proposed and put into practice, and is used for recording digitalbroadcast or the like. Optical discs are now establishing their positionas an important information medium (see “Zukai Blu-ray Disc Dokuhon”(Blu-ray Handbook with Diagrams) published by Ohmsha, Ltd.). For furtherincreasing the density, research and development is being performed forproviding a recording density higher than that of the BD to expand therecording capacity.

FIG. 17 shows an example of a conventional recording format. Recordingdata is recorded in units of blocks obtained by performing errorcorrection coding processing at every prescribed data amount. A blockincludes a run-in area used for synchronization detection duringreproduction provided at the start thereof, and a data area includingthe recording data. The data area is divided into a plurality ofsectors, and each sector is further divided into a plurality of frames.At the start of each frame, a frame synchronization pattern including aprescribed bit pattern and a synchronization ID pattern unique to therespective frame is located. After the frame synchronization pattern, abit pattern obtained by modulating the recording data in accordance witha prescribed modulation rule is recorded.

For the BD practically used today, the 1-7 modulation code is adopted,and the shortest bit length is 2T. The spatial frequency of 2T is closeto the limit of the optical resolving power and corresponds to 80% withrespect to the cutoff frequency of the optical transfer function (OTF)of the BD. Where the maximum amplitude detectable for various bitlengths is 100%, the amplitude of the reproduction signal of 2T is assmall as 10% thereof.

FIG. 18 shows the relationship between the optical resolving power ofthe BD and the shortest bit length 2T. When the shortest bit length isclose to the OTF cutoff frequency, proximate recording marks or evenproximate spaces are encompassed in the optical spot. Therefore, theamplitude of the reproduction signal is reduced and also the waveform isdistorted by the inter-code interference. Against such amplitudereduction and waveform distortion, the data detection precision isconventionally improved by using a PRML (Partial Response MaximumLikelihood) technology using an adaptive equalization technology and amaximum likelihood decoding technology such as Viterbi decoding.

FIG. 19 shows a structure of a conventional optical disc apparatus 1100.The optical disc apparatus 1100 includes an optical head 1001, a motor1002, a servo circuit 1003, an address reproducing circuit 1004, a CPU1005, a run-in generation circuit 1006, a data modulation circuit 1007,a recording control circuit 1008, a data signal extraction circuit 1009,a reproduction clock generation PLL circuit 1010, an adaptiveequalization circuit 1011, and a data demodulation circuit 1012. In thefigure, an optical disc 1000 on which data is recordable in areproduceable format is shown.

The optical head 1001 irradiates the optical disc 1000 with a light beamfor performing data recording or data reproduction. The motor 1002rotates the optical disc 1000 at a prescribed rotation rate.

Based on a reproduction signal obtained from the optical head 1001, theservo circuit 1003 appropriately controls the position of the opticalhead 1001 for outputting the light beam and the rotation rate of themotor 1002.

The address reproducing circuit 1004 reproduces address informationpre-recorded on a track of the optical disc 1000, which is included inthe detected reproduction signal.

The CPU 1005 controls the entire apparatus.

The run-in generation circuit 1006 generates a bit pattern for therun-in area.

The data modulation circuit 1007 generates a bit pattern obtained byperforming error correction coding processing and modulation onrecording data.

The recording control circuit 1008 controls the intensity of the lightbeam from the optical head 1001 such that the run-in bit pattern and thebit pattern of the recording data are recorded on a block at a specifiedaddress.

The data signal extraction circuit 1009 extracts a data signal based onthe recording data from the reproduction signal.

The reproduction clock generation PLL circuit 1010 generates areproduction clock bit-synchronized to the extracted data signal.

The adaptive equalization circuit 1011 appropriately binarizes the datasignal including amplitude reduction or wave distortion by the PRMLtechnology.

The data demodulation circuit 1012 performs demodulation and errorcorrection processing on the binarized data signal in accordance with aprescribed modulation rule to obtain reproduction data.

In order to effectively use the PRML technology in the adaptiveequalization circuit 1011, a reproduction clock signal acting as thereference for the operation timing of the adaptive equalization circuit1011 is required, and also the adaptive equalization circuit 1011 needsto perform adaptive locking control.

A reproduction clock signal is a clock signal synchronized to the bitlength of a data signal, and is generated by the reproduction clockgeneration PLL circuit 1010 which receives the data signal as an inputsignal. In order to generate a stable reproduction clock signal, it isusually appropriate that the response characteristic of the reproductionclock generation PLL circuit 1010 is set to a frequency which is aboutone several hundredths to one several tenths of an average spatialfrequency of a data signal.

In the meantime, data in the vicinity of the outermost end of theoptical disc 1000 may be reproduced by changing the position of theoptical disc 1000 to be irradiated with the light beam from the statewhere data in the vicinity of the innermost end of the optical disc 1000is being reproduced. For performing such reproduction, it is required todetect the synchronization position with respect to the data signalwithin a short time. This is required in order not to spoil theaccessibility to the data on the optical disc 1000 in the situationwhere the frequency of the bit length is significantly varied inaccordance with the rotation rate of the motor 1002 for rotating theoptical disc 1000 or in accordance with the radial position on theoptical disc 1000 of the data to be reproduced. For realizing this, thereproduction clock generation PLL circuit 1010 needs to have acapability of locking the frequency and the phase within a short time.

According to the conventional technology, in order to fulfill such arequirement by providing both the stability and the locking capabilityof the reproduction clock generation PLL circuit 1010 during datareproduction, a run-in area for allowing the reproduction clockgeneration PLL circuit 1010 to efficiently perform the locking isprovided at every prescribed block. As a bit pattern for the run-inarea, a single bit pattern shown in, for example, FIG. 17(A) is adopted.In this pattern, the same length bits of 4T marks and 4T spaces arecontinued. Since such a simple bit pattern is known in advance, afrequency error or a phase error can be easily detected and so thereproduction clock generation PLL circuit 1010 can perform the lockingstably in a short time.

The adaptive equalization circuit 1011 (FIG. 19) includes anequalization filtering circuit, an adaptive control circuit forcontrolling a filter coefficient of the equalization filtering circuit,and a Viterbi decoding circuit for binarizing an output from theequalization filtering circuit (none of these is shown).

The adaptive control circuit adaptively controls the filter coefficientof the equalization filtering circuit, such that the signal amplitude orthe wave distortion state of the data signal processed by theequalization filtering circuit reaches a target amplitude pre-specifiedfor each bit length, namely, such that the frequency characteristic ofthe data signal is close to the pre-specified frequency characteristic.The signal amplitude or the wave distortion state of the data signalmainly varies depending on the recording conditions, and therefore it isappropriate that the response characteristic of the adaptive controlcircuit for controlling the filter coefficient is set to be sufficientlylow. The adaptive control circuit is effective for a zone in which thesufficient locking control has been completed, but is not effective fora zone in which the locking control has not been completed. In such azone, a bit error is likely to occur during the data is decoded by theViterbi decoding circuit. Therefore, like the above-describedreproduction clock generation PLL circuit 1010, the adaptive controlcircuit needs to perform the locking control within a short time, suchthat when the position on the track of the optical disc 1000 at whichthe data is to be reproduced is changed, a stable data reduction stateis realized within a short time.

Conventionally, in order to fulfill such a requirement, the followingbit pattern is used as the bit pattern for the run-in area: a bitpattern by which all the pre-specified target amplitudes are present, inorder to allow the adaptive equalization circuit 1011 to perform theadaptive locking; and further a simple fixed bit pattern in order toallow, with certainty, the reproduction clock generation PLL circuit1010 to perform the locking.

FIG. 20 shows an ideal signal amplitude of each of signal waveforms of2T through 9T and synchronization sampling points by an idealreproduction clock signal, where the optical transfer function (OTF) isas shown in FIG. 18 and appropriate equalization processing has beenperformed. In the example shown here, as shown in FIG. 17(B), thefollowing three bit lengths are used: the shortest bit length 2T atwhich the reproduction signal amplitude is minimum, 3T at which thereproduction signal amplitude is at a medium level, 6T at which thereproduction signal amplitude is maximum. These three bit lengths areused in order to allow all the target amplitudes to be present.Furthermore, as a simple fixed bit pattern, a bit pattern having alength of 22T in total including 2T mark/2T space/3T mark/3T space/6Tmark/6T space is used, for example.

FIG. 21 shows an ideal signal waveform of a data signal of a repeat unitof 2T mark/2T space/3T mark/3T space/6T mark/6T space andsynchronization sampling points by an ideal reproduction clock signal.Owing to this, the reproduction clock generation PLL circuit 1010 canperform the locking and the adaptive equalization circuit 1011 canperform the adaptive locking control both in the run-in area, and so thedata recorded after the run-in area can be stably reproduced.

Recently, in order to respond to the demand for a significantly enlargedrecording capacity, studies are being made on optical discs having ahigher recording density than that of the conventional BD. It has beenfound that when the length of the recording marks and the inter-markdistances are decreased to obtain a larger recording capacity than theconventional recording capacity, the spatial frequency of the shortestbit length 2T becomes higher than the OTF cutoff frequency and as aresult, the amplitude of a 2T reproduction signal becomes 0%. Forexample, FIG. 22 shows an example in which the spatial frequency of 2Tis higher than the OTF cutoff frequency and the amplitude of a 2Treproduction signal is 0.

As seen from this example, when the bit pattern of a conventional run-inarea is used as it is for an optical disc having a higher density thanthe conventional recording density, the following problem arises. Thewaveform of a data signal corresponding to marks/spaces having a lengthof 2T or a length close to 2T is largely distorted and so an accuratebit border position cannot be obtained. As a result, the locking by thereproduction clock generation PLL circuit 1010 and the locking by theadaptive equalization circuit 1011 cannot be stably performed.

FIG. 23 shows an ideal signal amplitude of each of signal waveforms of2T through 9T and synchronization sampling points by an idealreproduction clock signal, where the optical transfer function (OTF) isas shown in FIG. 22 and appropriate equalization processing has beenperformed. The amplitude of each signal of 3T or longer is identifiablyobtained, but the signal amplitude of 2T is zero and is notidentifiable. FIG. 24 shows an ideal signal waveform of a data signal ofa repeat unit of 2T mark/2T space/3T mark/3T space/6T mark/6T space andsynchronization sampling points by an ideal reproduction clock signal insuch a case. It is seen that because the signal amplitude of 2T is zero,the mark/space bit border can be accurately obtained only at the borderbetween the 3T mark and the 3T space, the border between the 3T spaceand the 6T mark, and the border between the 6T mark and the 6T space. Inthe case where the 2T mark and the 2T space are not ideally recorded,the waveforms of 3T and 6T adjacent to 2T are largely distorted.Influenced by this, the border between the 3T mark and the 3T space andthe border between the 6T mark and the 6T space are shifted and cannotbe accurately obtained. In a worst case, neither the reproduction clockgeneration PLL circuit 1010 nor the adaptive equalization circuit 1011can perform the locking, and the data becomes unreproduceable.

The bit pattern of the conventional run-in area is a repetition of asimple fixed pattern. Therefore, there is another problem that thesynchronization for demodulating the data cannot be realized by the datademodulation circuit 1012 and data errors are continued in manyconsecutive zones. This may occur in the following case. An accurateposition in the run-in area cannot be specified, and so the locking bythe reproduction clock generation PLL circuit 1010 and the locking bythe adaptive equalization circuit 1011 are insufficient. As a result,the frame synchronization pattern of frame 0 which represents the startof data recorded after the run-in area cannot be detected.

SUMMARY OF THE INVENTION

The present invention made in light of the above-described problems hasan object of providing an optical disc having a bit pattern in a run-inarea, which allows a reproduction clock generation PLL circuit and anadaptive equalization circuit to perform stable locking even when thefrequency corresponding to the shortest bit length is higher than theOTF cutoff frequency, and which prevents the generation of continuousdata errors even when the locking by the reproduction clock generationPLL circuit or the locking by the adaptive equalization circuit isinsufficient. Another object of the present invention is to provide anoptical disc reproducing apparatus and an optical disc recordingapparatus using such a bit pattern in the run-in area.

An optical disc according to the present invention comprises tracks,each divided into a plurality of recording blocks; each of the pluralityof blocks includes a run-in area and a data area; in the run-in area, aprescribed run-in bit pattern is recordable; in the data area, bitpatterns having a plurality of bit lengths obtained by modulating dataas a recording target in accordance with a prescribed modulation ruleare recordable; at least one of spatial frequencies corresponding to thebit patterns having the plurality of bit lengths in accordance with theprescribed modulation rule is higher than a cutoff frequency; the cutofffrequency is defined as a frequency at which a gain of an opticaltransfer function (OTF) is 0 times; and the run-in bit patternrecordable in the run-in area includes the bit patterns having theplurality of bit lengths, from which the bit pattern corresponding tothe frequency higher than the OTF cutoff frequency has been excluded.

The run-in bit pattern may include the bit patterns having the pluralityof bit lengths, from which the bit pattern corresponding to thefrequency higher than the OTF cutoff frequency has been excluded, andwhich have a bit length equal to or shorter than a bit length at which areproduction signal of the run-in bit pattern, obtained from reflectedlight when the optical disc is irradiated with a prescribed light beam,has a maximum signal amplitude.

The run-in bit pattern may include both a combination of bit patternshaving a bit length difference of nT or smaller and a combination of bitpatterns having a bit length difference of (n+1) or larger, where n is anatural number.

In the run-in bit pattern, a part having a prescribed length from astart of the run-in area may include a pattern in which short bitlengths appear at a higher frequency than in a part immediately afterthe end of the prescribed length.

An optical disc according to the present invention comprises a trackdivided into a plurality of recording blocks; each of the plurality ofblocks includes a run-in area and a data area; in the run-in area, aprescribed run-in bit pattern is recordable; in the data area, bitpatterns having a plurality of bit lengths obtained by modulating dataas a recording target in accordance with a prescribed modulation ruleare recordable; where the shortest mark among the bit patterns havingthe plurality of bit lengths has a length of TM nm, the shortest spaceamong the bit patterns having the plurality of bit lengths has a lengthof TS nm, laser light used for irradiating the track has a wavelength ofλ nm, and an objective lens for collecting the laser light has anumerical aperture NA, TM+TS<λ/(2×NA) is fulfilled; and the run-in bitpattern recordable in the run-in area includes the bit patterns havingthe plurality of bit lengths, from which a bit pattern having a bitlength equal to or shorter than λ/(2×NA)/2 has been excluded.

The length λ of the laser light used for irradiating the track may be400 to 410 nm.

The numerical aperture NA of the objective lens may be 0.84 to 0.86.

A total length TM+TS of the length of the shortest mark and the lengthof the shortest space may be shorter than 238.2 nm (405/(2×0.85)).

The data as the recording target may be modulated by 1-7 modulationrule, the length of the shortest mark may be 2T and the length of theshortest space may be 2T.

A reproducing method according to the present invention is forreproducing data recorded on the above-described optical disc. Thereproducing method comprises the steps of detecting a reproductionsignal obtained by reproducing a bit pattern recorded on the track ofthe optical disc; generating a clock signal phase-synchronized to bitsof the reproduction signal; outputting a binary signal obtained byperforming adaptive equalization and then binarization on thereproduction signal; and demodulating the binary signal in accordancewith a prescribed modulation rule in the data area, thereby extractingrecording data. The step generating the clock signal performs lockingcontrol for phase synchronization on the reproduction signal and theclock signal in the run-in area at a higher gain than in the data area.The step of outputting the binary signal performs locking control foradaptive equalization in the run-in area at a higher gain than in thedata area.

A reproducing method according to the present invention is forreproducing data recorded on the above-described optical disc. Thereproducing method comprises the steps of detecting a reproductionsignal obtained by reproducing a bit pattern recorded on the track ofthe optical disc; generating a clock signal phase-synchronized to bitsof the reproduction signal; outputting a binary signal obtained byperforming adaptive equalization and then binarization on thereproduction signal; and demodulating the binary signal in accordancewith the prescribed modulation rule in the data area, thereby extractingrecording data. The step of generating the clock signal performs lockingcontrol for phase synchronization on the reproduction signal and theclock signal in the run-in area at a higher gain than in the data area.The step of outputting the binary signal performs locking control foradaptive equalization in the run-in area at a higher gain than in thedata area.

An optical disc recording method according to the present invention isfor recording recording data on the above-described optical disc. Theoptical disc recording method comprises the steps of generating therun-in bit pattern; generating a data bit pattern obtained by modulatingdata as the recording target in accordance with a prescribed modulationrule and then inserting a prescribed frame synchronization pattern atevery prescribed frame length; and recording the run-in bit pattern inthe run-in area, and recording the data bit pattern in the data area, ofeach of the recording blocks of the optical disc. The run-in bit patternincludes the bit patterns having the plurality of bit lengths, fromwhich a bit pattern corresponding to a frequency higher than the OTFcutoff frequency has been excluded.

An optical disc recording method according to the present invention isfor recording recording data on the above-described optical disc. Theoptical disc recording method comprises the steps of generating therun-in bit pattern; generating a data bit pattern obtained by modulatingdata as the recording target in accordance with a prescribed modulationrule and then inserting a prescribed frame synchronization pattern atevery prescribed frame length; and recording the run-in bit pattern inthe run-in area, and recording the data bit pattern in the data area, ofeach of the recording blocks of the optical disc. The run-in bit patternincludes the bit patterns having the plurality of bit lengths, fromwhich a bit pattern corresponding to a frequency higher than the OTFcutoff frequency has been excluded.

An optical disc according to the present invention comprises tracks,each divided into a plurality of recording blocks; each of the pluralityof blocks includes a run-in area and a data area; in the run-in area, aprescribed run-in bit pattern is recorded; and in the data area, a bitpattern, obtained by modulating recording data in accordance with aprescribed modulation rule and then inserting a prescribed framesynchronization pattern at every prescribed frame length, is recorded.The run-in bit pattern recorded in the run-in area includes a run-insynchronization pattern which includes a bit pattern longer than thelongest bit length included in the bit pattern recorded in the data areaand a bit pattern longer than the bit length of the framesynchronization pattern.

The run-in bit pattern may include a plurality of the run-insynchronization patterns, and the plurality of the run-insynchronization patterns are different bit patterns from each other.

A reproducing method according to the present invention is forreproducing the recording data from the above-described optical disc.The reproducing method comprises the steps of detecting a reproductionsignal obtained by reproducing a bit pattern recorded on the track ofthe optical disc; outputting a binary signal obtained by binarizing thereproduction signal; detecting a run-in synchronization pattern includedin the run-in area from the binary signal; detecting a framesynchronization pattern included in the data area from the binarysignal; and demodulating the binary signal in accordance with theprescribed modulation rule in the data area, thereby extracting therecording data. In the case where the run-in synchronization pattern isdetected by the run-in synchronization detection step in the run-in areaof each of the recording blocks but the frame synchronization pattern isundetectable by the frame synchronization detection step in the vicinityof the start of the data area following the run-in area, the step ofextracting the recording data performs demodulation processing on thedata area based on a timing at which the run-in synchronization patternis detected by the run-in synchronization detection step.

A recording method according to the present invention is for recordingthe recording data on the above-described optical disc. The recordingmethod comprises the steps of generating the run-in bit pattern;generating a data bit pattern obtained by modulating the recording datain accordance with a prescribed modulation rule and then inserting aprescribed frame synchronization pattern at every prescribed framelength; and recording the run-in bit pattern in the run-in area, andrecording the data bit pattern in the data area, of each of therecording blocks of the optical disc. The run-in bit pattern includes arun-in synchronization pattern which includes a bit pattern longer thanthe longest bit length included in the bit pattern recorded in the dataarea and a bit pattern longer than the bit length of the framesynchronization pattern.

In addition, in order to solve the above-described problems, an opticaldisc according to the present invention comprises a track divided into aplurality of recording blocks; each of the plurality of blocks includesa run-in area and a data area; in the run-in area, a prescribed run-inbit pattern is recorded; and in the data area, a bit pattern, obtainedby modulating recording data in accordance with a prescribed modulationrule and then inserting a prescribed frame synchronization pattern atevery prescribed frame length, is recorded. The run-in bit patternrecorded in the run-in area includes a run-in synchronization patternwhich includes a bit pattern which is longer than the longest bit lengthincluded in the bit pattern recorded in the data area and a bit patternlonger than the bit length of the frame synchronization pattern.

The run-in bit pattern may include a plurality of the run-insynchronization patterns, and the plurality of the run-insynchronization patterns may be different bit patterns from each other.

An optical disc according to the present invention comprises a trackdivided into a plurality of recording blocks; each of the plurality ofblocks includes a run-in area and a data area; in the run-in area, aprescribed run-in bit pattern is recorded; in the data area, bitpatterns obtained by modulating recording data in accordance with aprescribed modulation rule are recorded; the spatial frequencycorresponding to the shortest of the bit patterns in accordance with theprescribed modulation rule is higher than the cutoff frequency at whichthe OTF gain is 0 times; and the run-in bit pattern recorded in therun-in area includes the bit patterns generated by the prescribedmodulation rule, from which the bit pattern having a bit lengthcorresponding to the frequency higher than the OTF cutoff frequency hasbeen excluded.

The run-in bit pattern may include the bit patterns generated by theprescribed modulation rule, from which the bit pattern having a bitlength corresponding to the frequency higher than the OTF cutofffrequency has been excluded, and which have a bit length equal to orshorter than a bit length corresponding to a spatial frequency at whichthe OTF gain is maximum.

The run-in bit pattern may include both a combination of bit patternshaving a small bit length difference and a combination of bit patternshaving a large bit length difference.

In the run-in bit pattern, a first half may include a pattern in whichshort bit lengths appear at a high frequency.

An optical disc reproducing apparatus according to the present inventionis for reproducing recording data from an optical disc comprising atrack divided into a plurality of recording blocks; wherein each of theplurality of blocks includes a run-in area and a data area; in therun-in area, a prescribed run-in bit pattern is recorded; in the dataarea, a bit pattern, obtained by modulating the recording data inaccordance with a prescribed modulation rule and then inserting aprescribed frame synchronization pattern at every prescribed framelength, is recorded; and the run-in bit pattern recorded in the run-inarea includes a run-in synchronization pattern which includes a bitpattern which is longer than the longest bit length included in the bitpattern recorded in the data area and a bit pattern longer than the bitlength of the synchronization pattern. The optical disc reproducingapparatus comprises reproduction signal detection means for detecting areproduction signal obtained by reproducing a bit pattern recorded onthe track of the optical disc; binarization means for outputting abinary signal obtained by binarizing the reproduction signal; run-insynchronization detection means for detecting a run-in synchronizationpattern included in the run-in area from the binary signal; framesynchronization detection means for detecting a frame synchronizationpattern included in the data area from the binary signal; anddemodulation means for demodulating the binary signal in accordance withthe prescribed modulation rule in the data area, thereby extracting therecording data. In the case where the run-in synchronization pattern isdetected by the run-in synchronization detection means in the run-inarea of each of the recording blocks but the frame synchronizationpattern is undetectable by the frame synchronization detection means inthe vicinity of the start of the data area following the run-in area,the demodulation means performs demodulation processing on the data areabased on a timing at which the run-in synchronization pattern isdetected by the run-in synchronization detection means.

An optical disc reproducing apparatus according to the present inventionis for reproducing recording data from an optical disc comprising atrack divided into a plurality of recording blocks; wherein each of theplurality of blocks includes a run-in area and a data area; in therun-in area, a prescribed run-in bit pattern is recorded; in the dataarea, bit patterns obtained by modulating the recording data inaccordance with a prescribed modulation rule are recorded; the spatialfrequency corresponding to the shortest of the bit patterns inaccordance with the prescribed modulation rule is higher than the cutofffrequency at which the OTF gain is 0 times; and the run-in bit patternrecorded in the run-in area includes the bit patterns generated by theprescribed modulation rule, from which the bit pattern having a bitlength corresponding to the frequency higher than the OTF cutofffrequency has been excluded. The optical disc reproducing apparatuscomprises reproduction signal detection means for detecting areproduction signal obtained by reproducing a bit pattern recorded onthe track of the optical disc; clock generation means for generating aclock signal phase-synchronized to bits of the reproduction signal;adaptive equalization means for outputting a binary signal obtained byperforming adaptive equalization and then binarization on thereproduction signal; and demodulation means for demodulating the binarysignal in accordance with the prescribed modulation rule in the dataarea, thereby extracting the recording data. The clock generation meansperforms locking control for phase synchronization on the reproductionsignal and the clock signal in the run-in area at a higher gain than inthe data area. The adaptive equalization means performs locking controlfor adaptive equalization in the run-in area at a higher gain than inthe data area.

An optical disc recording apparatus according to the present inventionis for recording recording data on an optical disc comprising a trackdivided into a plurality of recording blocks; wherein each of theplurality of blocks includes a run-in area and a data area; in therun-in area, a prescribed run-in bit pattern is recorded; and in thedata area, a bit pattern, obtained by modulating the recording data inaccordance with a prescribed modulation rule and then inserting aprescribed frame synchronization pattern at every prescribed framelength, is recorded. The optical disc recording apparatus comprisesrun-in bit pattern generation means for generating the run-in bitpattern; data bit pattern generation means for generating a data bitpattern obtained by modulating the recording data in accordance with theprescribed modulation rule and then inserting a prescribed framesynchronization pattern at every prescribed frame length; and recordingmeans for recording the run-in bit pattern in the run-in area, andrecording the data bit pattern in the data area, of each of therecording blocks of the optical disc. The run-bit pattern generated bythe run-in bit pattern generation means includes a run-insynchronization pattern which includes a bit pattern longer than thelongest bit length included in the data bit pattern recorded in the dataarea and a bit pattern longer than the bit length of the framesynchronization pattern.

An optical disc recording apparatus according to the present inventionis for recording recording data on an optical disc comprising a trackdivided into a plurality of recording blocks; wherein each of theplurality of blocks includes a run-in area and a data area; in therun-in area, a prescribed run-in bit pattern is recorded; in the dataarea, bit patterns obtained by modulating the recording data inaccordance with a prescribed modulation rule are recorded; and thespatial frequency corresponding to the shortest of the bit patterns inaccordance with the prescribed modulation rule is higher than the cutofffrequency at which the OTF gain is 0 times. The optical disc recordingapparatus comprises run-in bit pattern generation means for generatingthe run-in bit pattern; data bit pattern generation means for generatinga data bit pattern obtained by modulating the recording data inaccordance with the prescribed modulation rule and then inserting aprescribed frame synchronization pattern at every prescribed framelength; and recording means for recording the run-in bit pattern in therun-in area, and recording the data bit pattern in the data area, ofeach of the recording blocks of the optical disc. The run-in bit patterngenerated by the run-in bit pattern generation means includes the bitpatterns generated by the prescribed modulation rule, from which a bitpattern having a bit length corresponding to a frequency higher than theOTF cutoff frequency has been excluded.

An optical disc reproducing method according to the present invention isfor reproducing recording data from an optical disc comprising a trackdivided into a plurality of recording blocks; wherein each of theplurality of blocks includes a run-in area and a data area; in therun-in area, a prescribed run-in bit pattern is recorded; in the dataarea, a bit pattern, obtained by modulating the recording data inaccordance with a prescribed modulation rule and then inserting aprescribed frame synchronization pattern at every prescribed framelength, is recorded; and the run-in bit pattern recorded in the run-inarea includes a run-in synchronization pattern which includes a bitpattern which is longer than the longest bit length included in the bitpattern recorded in the data area and a bit pattern longer than the bitlength of the frame synchronization pattern. The optical discreproducing method comprises a reproduction signal detection step ofdetecting a reproduction signal obtained by reproducing a bit patternrecorded on the track of the optical disc; a binarization step ofoutputting a binary signal obtained by binarizing the reproductionsignal; a run-in synchronization detection step of detecting a run-insynchronization pattern included in the run-in area from the binarysignal; a frame synchronization detection step of detecting a framesynchronization pattern included in the data area from the binarysignal; and a demodulation step of demodulating the binary signal inaccordance with the prescribed modulation rule in the data area, therebyextracting the recording data. In the case where the run-insynchronization pattern is detected by the run-in synchronizationdetection step in the run-in area of each of the recording blocks butthe frame synchronization pattern is undetectable by the framesynchronization detection step in the vicinity of the start of the dataarea following the run-in area, the demodulation step performsdemodulation processing on the data area based on a timing at which therun-in synchronization pattern is detected by the run-in synchronizationdetection step.

An optical disc reproducing method according to the present invention isfor reproducing recording data from an optical comprising a trackdivided into a plurality of recording blocks; wherein each of theplurality of blocks includes a run-in area and a data area; in therun-in area, a prescribed run-in bit pattern is recorded; in the dataarea, bit patterns obtained by modulating the recording data inaccordance with a prescribed modulation rule are recorded; the spatialfrequency corresponding to the shortest of the bit patterns inaccordance with the prescribed modulation rule is higher than the cutofffrequency at which the OTF gain is 0 times; and the run-in bit patternrecorded in the run-in area includes the bit patterns generated by theprescribed modulation rule, from which the bit pattern having a bitlength corresponding to the frequency higher than the OTF cutofffrequency has been excluded. The optical disc reproducing methodcomprises a reproduction signal detection step of detecting areproduction signal obtained by reproducing a bit pattern recorded onthe track of the optical disc; a clock generation step of generating aclock signal phase-synchronized to bits of the reproduction signal; anadaptive equalization step of outputting a binary signal obtained byperforming adaptive equalization and then binarization on thereproduction signal; and a demodulation step of demodulating the binarysignal in accordance with a prescribed modulation rule in the data area,thereby extracting the recording data. The clock generation stepperforms locking control for phase synchronization on the reproductionsignal and the clock signal in the run-in area at a higher gain than inthe data area. The adaptive equalization step performs locking controlfor adaptive equalization in the run-in area at a higher gain than inthe data area.

An optical disc recording method according to the present invention isfor recording recording data on an optical disc comprising a trackdivided into a plurality of recording blocks; wherein each of theplurality of blocks includes a run-in area and a data area; in therun-in area, a prescribed run-in bit pattern is recorded; and in thedata area, a bit pattern, obtained by modulating the recording data inaccordance with a prescribed modulation rule and then inserting aprescribed frame synchronization pattern at every prescribed framelength, is recorded. The optical disc recording method comprises arun-in bit pattern generation step of generating the run-in bit pattern;a data bit pattern generation step of generating a data bit patternobtained by modulating the recording data in accordance with theprescribed modulation rule and then inserting a prescribed framesynchronization pattern at every prescribed frame length; and arecording step of recording the run-in bit pattern in the run-in area,and recording the data bit pattern in the data area, of each of therecording blocks of the optical disc. The run-in bit pattern generatedby the run-in bit pattern generation step includes a run-insynchronization pattern which includes a bit pattern longer than thelongest bit length included in the data bit pattern recorded in the dataarea and a bit pattern longer than the bit length of the framesynchronization pattern.

An optical disc recording method according to the present invention isfor recording recording data on an optical disc comprising a trackdivided into a plurality of recording blocks; wherein each of theplurality of blocks includes a run-in area and a data area; in therun-in area, a prescribed run-in bit pattern is recorded; in the dataarea, bit patterns obtained by modulating the recording data inaccordance with a prescribed modulation rule are recorded; and thespatial frequency corresponding to the shortest of the bit patterns inaccordance with the prescribed modulation rule is higher than the cutofffrequency at which the OTF gain is 0 times. The optical disc recordingmethod comprises a run-bit pattern generation step of generating therun-in bit pattern; a data bit pattern generation step of generating adata bit pattern obtained by modulating the recording data in accordancewith the prescribed modulation rule and then inserting a prescribedframe synchronization pattern at every prescribed frame length; andrecording step of recording the run-in bit pattern in the run-in area,and recording the data bit pattern in the data area, of each of therecording blocks of the optical disc. The run-in bit pattern generatedby the run-in bit pattern generation step includes the bit patternsgenerated by the prescribed modulation rule, from which a bit patternhaving a bit length corresponding to a frequency higher than the OTFcutoff frequency has been excluded.

An integrated circuit according to the present invention is forreproducing recording data from a reproduction signal reproduced from anoptical disc comprising a track divided into a plurality of recordingblocks; wherein each of the plurality of blocks includes a run-in areaand a data area; in the run-in area, a prescribed run-in bit pattern isrecorded; in the data area, a bit pattern, obtained by modulating therecording data in accordance with a prescribed modulation rule and theninserting a prescribed frame synchronization pattern at every prescribedframe length, is recorded; and the run-in bit pattern recorded in therun-in area includes a run-in synchronization pattern which includes abit pattern which is longer than the longest bit length included in thebit pattern recorded in the data area and a bit pattern longer than thebit length of the frame synchronization pattern. The integrated circuitcomprises binarization means for outputting a binary signal obtained bybinarizing the reproduction signal; run-in synchronization detectionmeans for detecting a run-in synchronization pattern included in therun-in area from the binary signal; frame synchronization detectionmeans for detecting a frame synchronization pattern included in the dataarea from the binary signal; and demodulation means for demodulating thebinary signal in accordance with the prescribed modulation rule in thedata area, thereby extracting the recording data. In the case where therun-in synchronization pattern is detected by the run-in synchronizationdetection means in the run-in area of each of the recording blocks butthe frame synchronization pattern is undetectable by the framesynchronization detection means in the vicinity of the start of the dataarea following the run-in area, the demodulation means performsdemodulation processing on the data area based on a timing at which therun-in synchronization pattern is detected by the run-in synchronizationdetection means.

An integrated circuit according to the present invention is forreproducing recording data from a reproduction signal reproduced from anoptical disc comprising a track divided into a plurality of recordingblocks; wherein each of the plurality of blocks includes a run-in areaand a data area; in the run-in area, a prescribed run-in bit pattern isrecorded; in the data area, bit patterns obtained by modulating therecording data in accordance with a prescribed modulation rule arerecorded; the spatial frequency corresponding to the shortest the bitpatterns in accordance with the prescribed modulation rule is higherthan the cutoff frequency at which the OTF gain is 0 times; and therun-in bit pattern recorded in the run-in area includes the bit patternsgenerated by the prescribed modulation rule, from which the bit patternhaving a bit length corresponding to the frequency higher than the OTFcutoff frequency has been excluded. The integrated circuit comprisesclock generation means for generating a clock signal phase-synchronizedto bits of the reproduction signal; adaptive equalization means foroutputting a binary signal obtained by performing adaptive equalizationand then binarization on the reproduction signal; and demodulation meansfor demodulating the binary signal in accordance with the prescribedmodulation rule in the data area, thereby extracting the recording data.The clock generation means performs locking control for phasesynchronization on the reproduction signal and the clock signal in therun-in area at a higher gain than in the data area. The adaptiveequalization means performs locking control for adaptive equalization inthe run-in area at a higher gain than in the data area.

An integrated circuit according to the present invention is forgenerating a recording signal for recording recording data on an opticaldisc comprising a track divided into a plurality of recording blocks;wherein each of the plurality of blocks includes a run-in area and adata area; in the run-in area, a prescribed run-in bit pattern isrecorded; and in the data area, a bit pattern, obtained by modulatingthe recording data in accordance with a prescribed modulation rule andthen inserting a prescribed frame synchronization pattern at everyprescribed frame length, is recorded. The integrated circuit comprisesrun-in bit pattern generation means for generating the run-in bitpattern; data bit pattern generation means for generating a data bitpattern obtained by modulating the recording data in accordance with aprescribed modulation rule and then inserting a prescribed framesynchronization pattern at every prescribed frame length; and recordingmeans for recording the run-in bit pattern in the run-in area, andrecording the data bit pattern in the data area, of each of therecording blocks of the optical disc. The run-in bit pattern generatedby the run-in bit pattern generation means includes a run-insynchronization pattern which includes a bit pattern longer than thelongest bit length included in the bit pattern recorded in the data areaand a bit pattern longer than the bit length of the framesynchronization pattern.

An integrated circuit according to the present invention is forgenerating a recording signal for recording recording data on an opticaldisc comprising a track divided into a plurality of recording blocks;wherein each of the plurality of blocks includes a run-in area and adata area; in the run-in area, a prescribed run-in bit pattern isrecorded; in the data area, bit patterns obtained by modulating therecording data in accordance with a prescribed modulation rule arerecorded; and the spatial frequency corresponding to the shortest of thebit patterns in accordance with the prescribed modulation rule is higherthan the cutoff frequency at which the OTF gain is 0 times. Theintegrated circuit comprises run-in bit pattern generation means forgenerating the run-in bit pattern; data bit pattern generation means forgenerating a data bit pattern obtained by modulating the recording datain accordance with the prescribed modulation rule and then inserting aprescribed frame synchronization pattern at every prescribed framelength; and recording means for recording the run-in bit pattern in therun-in area, and recording the data bit pattern in the data area, ofeach of the recording blocks of the optical disc. The run-in bit patterngenerated by the run-in bit pattern generation means includes the bitpatterns generated by the prescribed modulation rule, from which the bitpattern having a bit length corresponding to the frequency higher thanthe OTF cutoff frequency has been excluded.

According to the present invention, a run-in synchronization patternhaving a longer bit length than the bit lengths present in the data areais located in the bit pattern in the run-in area. Owing to this, evenwhen the phase synchronization locking by the PLL circuit or theadaptive equalization locking by the adaptive equalization circuit isinsufficient, the run-in synchronization pattern having a long bitlength is easily detectable. Therefore, data following the run-in areabased on the run-in synchronization pattern detection position can bedemodulated. Thus, the generation of continuous data errors is avoided.

For performing high density recording with which the spatial frequencycorresponding to the shortest bit is higher than the cutoff frequency atwhich the OTF gain is 0 times, the run-in bit pattern recorded in therun-in area includes bit patterns generated by the prescribed modulationrule, from which the bit pattern having a bit length corresponding tothe frequency higher than the OTF cutoff frequency has been excluded.Owing to this, the positions of all the mark/space borders in the run-inbit pattern are easily obtained from the reproduction signal. Therefore,the locking by the PLL circuit and the locking by the adaptiveequalization circuit can be performed stably.

The run-in bit pattern includes the bit patterns generated by theprescribed modulation rule, from which the bit pattern having a bitlength corresponding to the frequency higher than the OTF cutofffrequency has been excluded, and which have a bit length equal to orshorter than a bit length corresponding to a spatial frequency at whichthe OTF gain is maximum. Alternatively, the run-in bit pattern includesboth a combination of bit patterns having a small bit length differenceand a combination of bit patterns having a large bit length difference.Owing to such a structure, the locking by the adaptive equalizationcircuit can be appropriately performed for bit patterns other than thebit pattern corresponding to a spatial frequency higher than the OTFcutoff frequency. Therefore, while data errors caused by a bit patterncorresponding to a low spatial frequency are suppressed, adaptiveequalization control can be stably performed on bit patternscorresponding to a spatial frequency higher than the OTF cutofffrequency.

In the run-in bit pattern, a first includes a pattern in which short bitlengths appear at a high frequency. In this case, there are manymark/space borders, and much timing information necessary for the PLLcircuit to control the phase of the channel clock signal and thereproduction signal is obtained. Thus, the locking control is madeeasier. After the locking by the PLL circuit is stabilized, a stablechannel clock signal can be used in a second half of the area to allowthe adaptive equalization circuit to perform the accurate locking.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a physical structure of an optical disc 1 according toEmbodiment 1.

FIG. 2 shows a recording format of the optical disc 1 according toEmbodiment 1.

FIG. 3 is a block diagram showing a structure of an optical discapparatus 250 according to Embodiment 2.

FIG. 4 is a timing diagram showing a recording operation of the opticaldisc apparatus 250.

FIG. 5 is a timing diagram showing a reproduction operation of theoptical disc apparatus 250.

FIG. 6 shows a recording format of an optical disc according toEmbodiment 3.

FIG. 7 is a block diagram showing a structure of an optical discapparatus 650 according to Embodiment 4.

FIG. 8 is a timing diagram showing a reproduction operation of theoptical disc apparatus 650.

FIG. 9 shows a recording format of an optical disc according toEmbodiment 5.

FIG. 10 shows a bit pattern combination having a length of 20T.

FIG. 11 shows a bit pattern combination having a length of 22T.

FIG. 12 shows a bit pattern combination having a length of 30T.

FIG. 13 shows a bit pattern combination having a length of 30T.

FIG. 14(A) shows an example of a BD having a conventional recordingdensity, and FIG. 14(B) shows an example of a disc having a higherdensity than that of the BD.

FIG. 15 shows a format of a block 153 of a BD.

FIG. 16 shows patterns of a run-out area and a guard area of the block153 in detail.

FIG. 17 shows an example of a conventional recording format.

FIG. 18 shows the relationship between the optical resolving power of aBD and the shortest bit length 2T.

FIG. 19 shows a structure of a conventional optical disc apparatus 1100.

FIG. 20 shows an ideal signal amplitude of each of signal waveforms of2T through 9T and synchronization sampling points by an idealreproduction clock signal, where the optical transfer function (OTF) isas shown in FIG. 18.

FIG. 21 shows an ideal signal waveform of a data signal of a repeat unitof 2T mark/2T space/3T mark/3T space/6T mark/6T space andsynchronization sampling points by an ideal reproduction clock signal.

FIG. 22 shows an example in which the spatial frequency of 2T is higherthan the OTF cutoff frequency and the amplitude of the reproductionsignal of 2T is 0.

FIG. 23 shows an ideal signal amplitude of each of signal waveforms of2T through 9T and synchronization sampling points by an idealreproduction clock signal, where the optical transfer function (OTF) isas shown in FIG. 22.

FIG. 24 shows an ideal signal waveform of a data signal of a repeat unitof 2T mark/2T space/3T mark/3T space/6T mark/6T space andsynchronization sampling points by an ideal reproduction clock signal.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinafter, embodiments of an optical disc and an optical discapparatus according to the present invention will be described.

Embodiment 1

FIG. 1 shows a physical structure of an optical disc 1 according to thisembodiment. On a discus-shaped optical disc 1, a great number of tracks2 are formed in a spiral, for example. On each track 2, a great numberof tiny sectors are formed. As described later, data is recorded on eachtrack 2 in units of blocks 3 having a predetermined size.

FIG. 2 shows a recording format of the optical disc 1 according to thisembodiment.

Data is recorded on the track 2 in units of blocks 3 obtained byperforming error correction coding processing at every prescribed dataamount. The track 2 is assigned block addresses on a block-by-blockbasis.

Each block 3 includes a run-in area 101 used for synchronizationdetection during reproduction provided at the start and a data area 102including recording data. The data area 102 is divided into a pluralityof sectors 103, and each sector 103 is further divided into a pluralityof frames 104. At the start of each frame 104, a frame synchronizationpattern 105 is located. After the frame synchronization pattern 105, abit pattern obtained by modulating the data to be recorded in accordancewith a prescribed modulation rule is recorded. A bit pattern isrepresented as a combination of bit lengths of 2T through 8T.

The frame synchronization pattern 105 includes a prescribed bit pattern(3T/9T/9T) and a synchronization ID pattern 106 having a prescribedlength. For making the frame synchronization pattern 105 identifiable,9T, which is not included in the bit pattern obtained by modulating therecording data, is used. 3T/9T/9T is detected and the synchronization IDpattern 106 after 3T/9T/9T is determined, and thus the frame number ofthe frame which is being reproduced can be specified.

The run-in area 101 is divided into three zones (bit patterns) 107 of aprescribed bit length. Between two adjacent zones, run-insynchronization pattern 0 or run-in synchronization pattern 1 isinserted.

The three zones 107 each include a plurality of 2T/2T/3T/3T/6T/6Tpatterns. Namely, this unit pattern is repeated.

The unit pattern includes “2T”. Therefore, when an optical discapparatus reproduces this repeat pattern, the following occurs. Wherethe spatial frequency of 2T is lower than the OTF cutoff frequency (FIG.18), a signal waveform as shown in FIG. 21 is obtained; whereas wherethe spatial frequency of 2T is higher than the OTF cutoff frequency(FIG. 22), a waveform as shown in FIG. 24 in which the amplitude of 2Tis zero is obtained.

As is clear from the above description, the bit length of the shortestbit pattern of the optical disc 1 according to this embodiment may bethe same as that of the conventional optical disc or shorter than thatof the conventional optical disc. In the case where the bit length ofthe shortest bit pattern of a recording mark of an optical disc is setto be shorter than that of the conventional optical disc, the recordingcapacity of such a disc per information recording layer is expanded ascompared with that of the conventional disc.

When bit synchronization is detected using the border position of therecorded mark and space in order to reproduce the optical disc 1, if theamplitude of 2T is zero, the following occurs. The position of a borderrelating to 2T cannot be used to detect the bit synchronization, and soinformation required to detect the bit synchronization is insufficient.If the bit synchronization cannot be accurately detected in a run-inarea, the frame synchronization pattern of frame 0 at the start of thedata area cannot be detected. As a result, data in the first one frameor the first two frames is erroneous.

In order to avoid this, in this embodiment shown in FIG. 2, three zones107 are provided in the run-in area 101; and further run-insynchronization pattern 0 is provided between the first zone and thesecond zone, and run-in synchronization pattern 1 is provided betweenthe second zone and the third zone. The run-in synchronization patternsare provided in this manner in order to ensure that the run-in area 101is detectable. In this embodiment, a plurality of relatively long bitpatterns are provided as run-in synchronization pattern 0 and run-insynchronization pattern 1. Thus, the optical disc apparatus is unlikelyto make an incorrect detection.

Since the run-in synchronization pattern 0 is provided between the firstand second zones and run-in synchronization pattern 1 is providedbetween the second and third zones, the optical disc apparatus canspecify, with certainty, data at which position is currently being read.Thus, an incorrect detection can be prevented with higher certainty.

Now, a run-in synchronization pattern will be described in more detail.

In this embodiment, run-in synchronization pattern 0 is a bit pattern of13T/13T/11T/11T/6T/6T, and run-in synchronization pattern 1 is a bitpattern of 13T/11T/11T/13T/6T/6T, 13T and 11T, which have longer bitlengths than those used in the frame synchronization pattern in the dataarea, are used, and there is a bit length difference of 2T in theserun-in synchronization patterns. Owing to this, even if the bitsynchronization frequency is shifted at a certain point, patterndetection and bit synchronization position detection can be accuratelyperformed.

The run-in synchronization patterns are largely different from therepeat pattern and are inserted at prescribed positions. Therefore, therun-in synchronization patterns can be detected out of the run-in bitpatterns. The start position of frame 0 can be easily estimated from thedata which is being reproduced from the run-in area instead of the dataarea. In addition, there are two run-in synchronization patterns.Therefore, even if run-in synchronization pattern 0 is undetectable, aslong as run-in synchronization pattern 1 is detectable, the startposition of frame 0 can be estimated. Using both of the run-insynchronization patterns, the probability of the start position of frame0 being accurately estimated can be further improved.

In the above-described embodiment, an example of the structure of therecording format and an example of the bit pattern in the run-in areaare provided. The present invention is not limited to these.

Embodiment 2

FIG. 3 is a block diagram showing a structure of an optical discapparatus 250 according to this embodiment.

The optical disc apparatus 250 shown in FIG. 3 is capable of bothreproducing data from an optical disc 200 and recording data to theoptical disc 200. This is merely an example, and the optical discapparatus 250 only needs to be capable of performing at least one ofdata reproduction and data recording.

The optical disc apparatus 250 includes an optical head 201, a motor202, a servo circuit 203, an address reproducing circuit 204, a CPU 205,a run-in generation circuit 206, a data modulation circuit 207, arecording control circuit 208, a data signal extraction circuit 209, areproduction clock generation PLL circuit 210, an adaptive equalizationcircuit 211, a data demodulation circuit 212, and a run-insynchronization detection circuit 213.

The servo circuit 203, the address reproducing circuit 204, the CPU 205,the run-in generation circuit 206, the data modulation circuit 207, therecording control circuit 208, the data signal extraction circuit 209,the reproduction clock generation PLL circuit 210, the adaptiveequalization circuit 211, the data demodulation circuit 212, and therun-in synchronization detection circuit 213 are mounted as a one-chipcircuit (optical disc controller) 240. It is not necessary that allthese elements are incorporated into one chip. For example, the servocircuit 230 does not need to be incorporated. The address reproducingcircuit 204 may be incorporated into the optical head 201.Alternatively, these elements may be provided as separate circuitsinstead of being incorporated into one chip.

The optical disc 200 has a track on which data is recordable, and datais recorded on the track in accordance with the recording formatdescribed above in Embodiment 1 of the present invention. The opticaldisc 200 is dismountable from the optical disc apparatus 250, and is notan element of the optical disc apparatus 250.

The optical disc 201 irradiates the optical disc 200 with a light beam,detects an amount of light reflected from the optical disc 200 whilescanning the track, and outputs an electric signal.

The motor 202 rotates the optical disc 200 at a specified rotation rate.

The servo circuit 203 extracts, from the electric signal, a servo errorsignal in accordance with the light collection state of the light beamon the track, and performs control using the servo error signal suchthat the light collection state of the light beam from the optical head201 on the track and the scanning state of the track are optimal. Theservo circuit 203 also controls the radial position on the optical disc200 to be irradiated with the light beam and the rotation rate of themotor 202 to be optimal.

The address reproducing circuit 204 extracts, from the electric signal,an address signal including address information pre-recorded on thetrack of the optical disc 200, reproduces the address information fromthe address signal, and also detects a synchronization position to theblock on the track of the optical disc 200.

The CPU 205 perform a search to find a block to/from which data is to berecorded/reproduced while obtaining the address information from theaddress reproducing circuit 204, and issues an instruction on arecording operation or a reproduction operation. The data is recorded onthe optical disc 200 by the run-in generation circuit 206, the datamodulation circuit 207, and the recording control circuit 208. The datais reproduced by the data signal extraction circuit 209, thereproduction clock generation PLL circuit 210, the adaptive equalizationcircuit 211, the data demodulation circuit 212, and the run-insynchronization detection circuit 213.

Now, a recording operation of the optical disc apparatus 250 will bedescribed. FIG. 4 is a timing diagram showing the recording operation ofthe optical disc apparatus 250.

The run-in generation circuit 206 generates a run-in area bit pattern tobe recorded in the run-in area. The run-in area bit pattern is the bitpattern shown in the run-in area 101 in FIG. 2 described above inEmbodiment 1. The bit pattern is output to the recording control circuit208 in a zone of the run-in area based on the block synchronizationposition detected by the address reproducing circuit 204.

As a preparation for the recording data, the data modulation circuit 207generates error correcting code (ECC) data obtained by performingprescribed error correction coding processing on the recording data.During execution of the recording, the data modulation circuit 207sequentially modulates the ECC data in accordance with a prescribedmodulation rule. For performing the modulation, the data modulationcircuit 207 inserts a frame synchronization pattern to each frame. Thegenerated data area bit pattern is output to the recording controlcircuit 208 in a zone of the data area based on the blocksynchronization position detected by the address reproducing circuit204.

Upon receiving an instruction to perform on recording from the CPU 205,the recording control circuit 208 selects, as a recording signal, therun-in area bit pattern obtained from the run-in generation circuit 206in the run-in area of the block having a specified address, and selects,as a recording signal, the data area bit pattern obtained from the datamodulation circuit 207 in the data area of such a block. The recordingcontrol circuit 208 controls the intensity of the light beam to beoutput from the optical head 201 based on the recording signal, and thusrecords the bit pattern to a prescribed block of the optical disc 200.

Now, a reproduction operation of the optical disc apparatus 250 will bedescribed. FIG. 5 is a timing diagram showing the reproduction operationof the optical disc apparatus 250.

The data signal extraction circuit 209 extracts a data signal(“reproduction signal” in the figure) in accordance with the marks andspaces recorded on the track of the optical disc 200, from the electricsignal detected by the optical head 201.

The reproduction clock generation PLL circuit 210 generates areproduction clock signal phase-synchronized to the data signal. Asshown in “PLL control” of FIG. 5, the reproduction clock generation PLLcircuit 210 is in a hold state in an unrecorded zone in which no data isrecorded.

When the reproduction signal goes into a state in which the reproductionsignal includes information on the run-in area of the block in whichdata is recorded, the “PLL control” is put into a state of performing alocking operation. First, using the repeat pattern of the run-in bitpattern, frequency locking is performed as shown in “reproduction signalfrequency” of FIG. 5. When the frequencies substantially match eachother, phase locking is performed so as to synchronize the phases. Thephase locking is completed by a position immediately before the dataarea. After this, the phase locked state is maintained in the data area.

When the recording density of the optical disc 200 is such that thespatial frequency of 2T is lower than the OTF cutoff frequency as shownin FIG. 18, the positions of all the mark/space borders are obtained inthe data signal in the run-in area as shown in FIG. 21. Therefore, asufficient control gain is obtained by the reproduction clock generationPLL circuit 210. Owing to this, as shown as a change of “reproductionclock frequency” of FIG. 5, the locking capability is high and both thefrequency locking and the phase locking can be completed at an earlystage of the run-in area. Thus, a sufficient extra time can be obtainedbefore the timing of the start position of the data area.

By contrast, when the recording density of the optical disc 200 is suchthat the spatial frequency of 2T is higher than the OTF cutoff frequencyas shown in FIG. 22, the positions of the mark/space borders relating to2T are not obtained in the data signal in the run-in area as shown inFIG. 24. Therefore, the control gain of the reproduction clockgeneration PLL circuit 210 is insufficient. The signal waveform islikely to be distorted due to inter-code interference. Therefore, thegain needs to be still lower in order to stabilize the reproductionclock generation PLL circuit 210. As a result, as shown as a change of“reproduction clock frequency” of FIG. 5, the locking capability is lowand the frequency locking and the phase locking both require a longtime. Thus, it is difficult to obtain a sufficient extra time before thetiming of the start position of the data area.

In this embodiment, the above problems are solved by use of the adaptiveequalization circuit 211. The adaptive equalization circuit 211 performsthree types of processing, i.e., equalization filtering processing,adaptive control processing of a filter coefficient of the equalizationfiltering circuit, and Viterbi decoding processing of binarizing anoutput from the equalization filtering circuit. These types ofprocessing may be implemented as software processing or as circuitsperforming the respective processing. In the following, these types ofprocessing is each implemented as a respective circuit.

When the spatial frequency of 2T is lower than the OTF cutoff frequency(FIG. 18), the target of the output signal from the equalizationfiltering circuit is that the signal amplitude of each of 2T through 9Tand the sampling points by the reproduction clock signal realize thestate of the waveform diagram shown in FIG. 20. The adaptive controlcircuit controls the filter coefficient such that the amplitude and thephase of the output signal from the equalization filtering circuit areclose to the target levels. The Viterbi decoding circuit compares theoutput signal from the equalization filtering circuit and the targetwaveform shown in FIG. 20 to perform maximum likelihood decoding andoutputs the result as a binary signal binarized into a mark and a space.

When the frequency of the data signal and the frequency of thereproduction clock signal are largely dispersed, an error of theamplitude and the phase with respect to the target levels cannot beaccurately found. Therefore, as shown in “adaptive equalization control”of FIG. 5, the operation of the adaptive control circuit is on holduntil a prescribed timing at which the locking operation by thereproduction clock generation PLL circuit 210 is estimated to becompleted. At the prescribed timing, the adaptive control circuit isreleased from the held state and starts the locking for adaptiveequalization control. The adaptive control circuit operates so as tocomplete the locking in the vicinity of the start of the data area andthen maintain the locked state.

By contrast, when the recording density of the optical disc 200 ishigher and so the spatial frequency of 2T is higher than the OTF cutofffrequency (FIG. 22), the locking capability of the reproduction clockgeneration PLL circuit 210 is low. Therefore, an error is likely tooccur also in the control performed by the adaptive equalization circuitand the locking operation is not stable. Accordingly, until the adaptivecontrol circuit completes the locking in a sufficient state, the binarysignal output from the Viterbi decoding circuit also includes manyerrors.

When the recording density is increased as described above, thefollowing occurs in a worst case. Since the locking performed by thereproduction clock generation PLL circuit 210 and the locking performedby the adaptive equalization circuit 211 are not completed within therun-in area, the frame synchronization pattern of frame 0 cannot bedetected. As a result, all the data in frames 1 and 2 or the like iserroneous.

In order to avoid this, the run-in synchronization detection circuit 213detects run-in synchronization pattern 0 and run-in synchronizationpattern 1 shown in FIG. 2, and outputs a run-in synchronization patterndetection signal. The run-in synchronization pattern is detecteddepending on the 13T and 11T part. When the length ratio is 3:13:11:11,the run-in synchronization pattern is detected as run-in synchronizationpattern 0. When length ratio is 13:11:11:13, the run-in synchronizationpattern is detected as run-in synchronization pattern 1. The run-insynchronization pattern 0 and run-in synchronization pattern 1 areclearly different from the repeat pattern located therebefore andthereafter, and are bit patterns corresponding to a sufficiently lowerspatial frequency than the OTF cutoff frequency and so are unlikely tobe influenced by the inter-code interference. Even when the lockedstates realized by the reproduction clock generation PLL circuit 210 andthe adaptive equalization circuit 211 are insufficient as describedabove, these run-in synchronization patterns are easily detectable. Therun-in synchronization patterns each have a length of 60T. The last 6Tpart is immediately followed by 2T of the repeat pattern and so islikely to be influenced by the waveform distortion. Even with this 6Tpart being excluded, the run-in synchronization patterns have a lengthof 54T, which is sufficient to detect a frequency error of about 1.85%or higher and thus to correct the error of the reproduction clockgeneration PLL circuit 210.

The data demodulation circuit 212 detects the frame synchronizationpattern from the binary signal which is output from the adaptiveequalization circuit 211 to operate a frame synchronization demodulationcounter which has been frame-synchronized, and demodulates the binarysignal in accordance with a prescribed modulation rule at the timingprovided by the frame synchronization demodulation counter. Then, thedata demodulation circuit 212 performs prescribed error correctionprocessing on the obtained one block of demodulated data to correct theerror thereof, and outputs the obtained data as reproduction data.

If the locked states realized by the reproduction clock generation PLLcircuit 210 and the adaptive equalization circuit 211 are insufficientand so the frame synchronization pattern of frame 0 is undetected by thedata demodulation circuit 212, the frame synchronization demodulationcounter is not preset to a correct timing. Therefore, until the datademodulation circuit 212 detects the frame synchronization pattern offrame 1 or frame 2 and presets the frame synchronization demodulationcounter to a correct timing, all the demodulated data is erroneous. Inorder to avoid this, the run-in synchronization pattern detection signalis used to preset the frame synchronization demodulation counter at thedetection timing of run-in synchronization pattern 0 and run-insynchronization pattern 1 in the run-in area. Owing to this, even if theframe synchronization pattern of frame 0 is undetected, the demodulationprocessing is performed at a correct timing because the framesynchronization demodulation counter has already been preset to acorrect timing by the run-in synchronization pattern. Therefore, thedemodulated data can be prevented from being erroneous continuously.

In the above-described embodiment, the optical disc apparatus 250compatible to the above-described examples of the structure of therecording format and the bit pattern in the run-in area is provided. Thepresent invention is not limited to this.

In the above-described embodiment, an example of the target equalizationlevel for the adaptive equalization circuit are provided. The presentinvention is not to this.

Embodiment 3

FIG. 6 shows a recording format of an optical disc according to thisembodiment. The format shown in this figure is different from the formatshown in FIG. 2 in a run-in area 501 included in the block 3. The dataarea 102 shown in FIG. 6 is the same as the data shown in FIG. 2, and sowill not be described. The external structure of the optical disc inthis embodiment is the same as the optical disc 1 shown in FIG. 1according to Embodiment 1.

In addition, the optical disc according to this embodiment is structuredsuch that the spatial frequency of the shortest bit length 2T is 1.12times of the OTF cutoff frequency as shown in FIG. 22.

The run-in area 501 is divided into two areas 507 and 508. The bitpattern in a first area 507 is repeat pattern A shown in FIG. 6, and thebit pattern in a second area 508 is repeat pattern B shown in FIG. 6.

Pattern A in the first area includes a repetition of 4T/4T/5T/5T.Neither 2T, corresponding to a frequency exceeding the OTF cutofffrequency, nor 3T, corresponding to a spatial frequency close to the OTFcutoff frequency and a small amplitude, is used. A long bit length,which reduces a mark/space border area acting as control information forthe reproduction clock generation PLL circuit of an optical discapparatus, is not used. Owing to these, the control performed by thereproduction clock generation PLL circuit is made easier. An operationof the optical disc apparatus will be described in detail in Embodiment4.

Repeat pattern B in the second area includes a repetition of3T/4T/5T/6T/7T/7T/6T/5T/4T/3T/7T/3T/7T/7T/3T/7T/6T/3T/6T/6T/3T/6T. Likein repeat pattern A, 2T, corresponding to a spatial frequency exceedingthe OTF cutoff frequency, is not used. In a first half of this repeatunit, bit lengths close to each other are combined; whereas in a secondhalf of this repeat unit, long bit lengths and short bit lengths arecombined.

For example, where 3T, 4T, etc. is referred to as one pattern, in a partfrom the first until the tenth patterns (first half), combinations ofbit lengths which are different by 1T or smaller are provided. In a partfrom the eleventh pattern until the end (second half), combinations ofbit lengths which are different by 2T or larger are provided. From theeleventh pattern to the end, the difference does not always need to be2T or greater. As shown in FIG. 6, 7T and 7T, or 6T and 6T, may beadjacent to each other, or 7T and 6T may be adjacent to each other.

More generally, where n is a natural number, repeat pattern B may bedetermined so as to include a combination of bit patterns having a bitlength difference of nT or smaller and a combination of bit patternshaving a bit length difference of (n+1) or larger.

The above-mentioned definition of “first half” and “second half” is oneexample. More generally, the “first half” means a part of a predefinedlength (prescribed length) from the start of the run-in bit pattern, andthe “second half” means a part from a position immediately after theprescribed length counted from the start of the run-in bit pattern untilthe end of the run-in bit pattern.

Combinations of marks and spaces in which inter-code interference mayoccur are roughly classified into a combination of a mark and a spacehaving bit lengths close to each other, a combination of long bit lengthspaces (or marks) and a short bit length mark (or space) sandwichedtherebetween, and a combination involving 2T which causes the amplitudeof the signal waveform to be zero (FIG. 23). In the locking stage foradaptive equalization of the optical disc apparatus, a waveforminvolving 2T having an undetectable amplitude is likely to bemisrecognized and reduces the stability of locking. The stability can beimproved by performing the locking on the other two combinations inwhich inter-code interference may occur and then performing adaptiveequalization on all the combinations including the one involving 2T.

Pattern A having a combination of bit lengths close to each other isadopted in the first half of the repeat unit, so that the adaptiveequalization circuit of the optical disc apparatus can perform thelocking for adaptive equalization control on the inter-code interferencestate of pattern A. By contrast, pattern B having a combination of bitlengths far from each other is adopted in the second half of the repeatunit, so that the optical disc apparatus can perform the locking foradaptive equalization control on the inter-code interference state ofpattern B. In this manner, in the zone having pattern B, appropriateadaptive equalization can be performed against the inter-codeinterference on the bit length combinations excluding the combinationinvolving 2T, corresponding to a spatial frequency exceeding the OTFcutoff frequency.

Owing to the above-described run-bit patterns, the reproduction clockgeneration PLL circuit first performs a locking operation using repeatpattern A, and then the adaptive equalization circuit performs a lockingoperation for adaptive equalization using repeat pattern B. After bothof the locking operations are completed, the reproduction operation fromthe data area can be performed. The adaptive equalization on thewaveform involving 2T is not performed. Nonetheless, this does not causea reproduction error because the adaptive equalization has beenappropriately performed on the waveforms except for the waveforminvolving 2T. In addition, in the data area, the adaptive equalizationcontrol has been performed on the waveforms involving 2T. Therefore, thereproduction capability can be further stabilized.

In the above-described embodiment, an example of the structure of therecording format and examples of the bit pattern in the run-in area areprovided. The present invention is not limited to these.

Embodiment 4

FIG. 7 is a block diagram showing a structure of an optical discapparatus 650 according to this embodiment.

The optical disc apparatus 650 shown in FIG. 7 is capable of bothreproducing data from an optical disc 600 and recording data to theoptical disc 600. This is merely an example, and the optical discapparatus 650 only needs to be capable of performing at least one ofdata reproduction and data recording.

The optical disc apparatus 650 includes an optical head 601, a motor602, and an optical disc controller 640. The optical disc controller 640includes a servo circuit 603, an address reproducing circuit 604, a CPU605, a run-in generation circuit 606, a data modulation circuit 607, arecording control circuit 608, a data signal extraction circuit 609, areproduction clock generation PLL circuit 610, an adaptive equalizationcircuit 611, and a data demodulation circuit 612.

The optical disc 600 has a track on which data is recordable, and datais recorded on the track in accordance with the recording formatdescribed in Embodiment 3. As in Embodiment 3, the spatial frequency of2T is higher than the OTF cutoff frequency and is 1.12 times thereof.

The elements of the optical disc apparatus 650 in FIG. 7 which areidentical with those in Embodiment 2 or Embodiment will not bedescribed. The elements other than the elements described below have thesame functions as those of the elements with the same names shown inFIG. 3.

First, processing performed by the run-in generation circuit 606relating to the data recording operation to the optical disc 600 will bedescribed.

The run-in generation circuit 606 generates a run-in area bit pattern tobe recorded in the run-in area 501 (FIG. 6). The run-in area bit patternis the bit pattern shown in the run-in area 501 in FIG. 6 describedabove in Embodiment 3. The bit pattern is output to the recordingcontrol circuit 608 in a zone of the run-in area based on the blocksynchronization position detected by the address reproducing circuit604. The recording control circuit 608 controls the intensity of thelight beam to be output from the optical head 601 such that the run-inbit pattern is recorded in the run-in area.

Now, an operation of each of the reproduction clock generation PLLcircuit 610 and the adaptive equalization circuit 611 relating to thereproduction operation from the optical disc 600 will be described.

FIG. 8 is a timing diagram showing the reproduction operation of theoptical disc apparatus 650.

The address reproducing circuit 604 instructs the reproduction clockgeneration PLL circuit 610 to perform a locking operation at a high gainin the zone of the run-in area in which repeat pattern A is recordedbased on the detected block synchronization position, and to maintainthe phase-locked state at a low gain after the locking operation isfinished.

In accordance with the instruction from the address reproducing circuit604, the reproduction clock generation PLL circuit 610 operates so as toperform a locking operation at a high gain in the zone of repeat patternA, and so as to maintain the phase-locked state at a low gainthereafter. Repeat pattern A is a simple repeat pattern of 4T/4T/5T/5T.Therefore, in the zone of repeat pattern A, the comparison offrequencies is relatively easy, and a stable locking operation can beperformed within a short time by using a high gain.

From “PLL control” of FIG. 8, it is understood that the locked state ismaintained in the zone in which repeat pattern A is recorded and thatthe phase-locked state is maintained in the zone in which repeat patternB is recorded.

In accordance with the instruction from the address reproducing circuit604, the adaptive equalization circuit 611 issues an instruction to holdthe operation in the zone in which repeat pattern A is recorded (duringthe locking operation of the reproduction clock generation PLL circuit610), issues an instruction to perform the locking operation at a highgain in the zone in which repeat pattern B is recorded, and issues aninstruction to maintain the locked state of the adaptive equalizationcontrol at a low gain thereafter (“adaptive equalization control”) ofFIG. 8.

Repeat pattern B does not include 2T, which causes the locking to beunstable. Therefore, the locking operation can be performed at a highgain with no problem, and stable locking can be realized within a shorttime.

By the combination pattern of the first half of the repeat unit ofrepeat pattern B, the adaptive equalization control is performed so asto correct the distortion of a signal waveform caused by the influenceof inter-code interference between bit lengths close to each other. Bythe combination pattern of the second half of the repeat unit, theadaptive equalization control is performed so as to also correct thedistortion of a signal waveform caused by the influence of inter-codeinterference between bit lengths far from each other. In this manner,the locking for adaptive equalization is performed, in the zone ofrepeat pattern B, against the influence of the inter-code interferencesother than the inter-code interference relating to 2T. Thus, acapability of correctly binarizing a data signal can be obtained. In thedata area, control is performed to maintain the stable state at a lowgain while appropriately performing adaptive equalization also againstthe influence of the inter-code interference relating to 2T.

According to the above-described processing, as shown in “framesynchronization pattern detection” of FIG. 8, the frame 0synchronization pattern at the start of the data area can be stablydetected. As a result, as shown in “frame synchronization demodulationcounter” of FIG. 8, the frame synchronization demodulation counter inthe data demodulation circuit 612 can be operated at a correct timingand thus the data demodulation error can be suppressed to be minimum.

In the above-described embodiment, examples of the structure of therecording format and examples of the bit pattern in the run-in area areprovided. The present invention is not limited to these.

Embodiment 5

FIG. 9 shows a recording format of an optical disc according to thisembodiment. The data structure of this optical disc is similar to thedata structure shown in FIG. 6.

Data is recorded in units of blocks obtained by performing errorcorrection coding processing at every prescribed data amount.

A block includes a run-in area used for synchronization detection duringreproduction provided at the start thereof and a data area including therecording data. The data area is divided into a plurality of sectors,and each sector is further divided into a plurality of frames. At thestart of each frame, a frame synchronization pattern including aprescribed bit pattern and a synchronization ID pattern unique to therespective frame is located. After the frame synchronization pattern, abit pattern obtained by modulating the recording data in accordance witha prescribed modulation rule is recorded and is represented by acombination of 2T through 8T.

The optical disc according to this embodiment is structured such thatthe spatial frequency of the shortest bit length 2T is 1.12 times of theOTF cutoff frequency as shown in FIG. 22.

The frame synchronization pattern includes 3T/9T/9T and asynchronization ID pattern having a prescribed length. The framesynchronization pattern is distinguishable by using 9T, which is notincluded in the bit pattern obtained by modulating the recording data.3T/9T/9T is detected and the synchronization ID pattern after 3T/9T/9Tare determined, and thus the frame number of the frame which is beingreproduced can be determined.

The run-in area has a length of 2640T, and a prescribed bit pattern isrecorded therein.

FIG. 10, FIG. 11, FIG. 12 and FIG. 13 each show repeat bit patterns forthe run-in area. The run-in bit pattern in the conventional optical discis 2T/2T/3T/3T/6T/6T having a total length of 22T as shown in FIG. 24,and this bit pattern is recorded 120 times in repetition in the run-inarea.

However, as shown in FIG. 22, when the spatial frequency of the shortestbit length 2T is higher than the OTF cutoff frequency, the amplitude ofthe 2T part is not obtained as shown in FIG. 24 by the conventionalrun-in bit pattern. As a result, the PLL or PRML control performed atthe time of reproduction is made unstable. Therefore, a bit patternincluding 2T is not desirable.

The bit patterns shown in each of FIGS. 10 through 13 do not include 2Tcorresponding to a spatial frequency higher than the OTF cutofffrequency and includes 3T through 8T corresponding to a spatialfrequency lower than the OTF cutoff frequency. Owing to this, the PLL orPRML control performed at the time of reproduction can be made stablewith certainty.

When a bit pattern including a 5T or longer pattern, at which themaximum amplitude of a reproduction signal is obtained, is used as shownin FIG. 23, the reproduction signal amplitude control can beappropriately performed at the time of reproduction.

The bit pattern combinations shown in FIG. 11 have a length of 22T likethe bit pattern of the conventional optical disc. The bit patterncombinations shown in FIG. 10 have a length of 20T, which is a divisorof 2640T, i.e., the length of the run-in area. The bit patterncombinations shown in FIG. 12 and FIG. 13 have a length of 30T, which isalso a divisor of 2640T. The lengths of the bit patterns are differentbut are all divisors of the length of the run-in area. Therefore, thelength of one block including the data area is not changed and thus thecompatibility with the recording format of the conventional optical disccan be easily obtained.

As shown in each of FIGS. 10 through 13, there are a plurality of usablebit patterns. For reproducing recorded data, reproduction signalamplitude control, PLL locking control and adaptive equalization lockingcontrol each need to be stably performed. For the amplitude control, itis preferable that the maximum amplitude is obtained at a highfrequency. For the PLL locking control, it is preferable that shortmark/short space combinations appear at a high frequency because thegain is obtained more easily when the number of change points of thereproduction signal is larger. For the adaptive equalization lockingcontrol, it is preferable that the equalization levels shown in FIG. 23are obtained at a uniform frequency in order to appropriately convergethe equalized states. Especially in the case of a high recording densityat which the shortest mark/space corresponds to a spatial frequencyhigher than the OTF cutoff frequency, the adaptive equalizationtechnology is indispensable. In order to stably reproduce the recordeddata, adaptive equalization locking control is important. In order tofulfill the above conditions at a good balance, a bit pattern, in whichthe frequency of appearance of three sets of bit lengths, i.e., 3T, 4Tthrough 5T, and 6T through 8T, is substantially uniform, and the marklength and the space length are equal to make the DC component zero, isdesirable.

Especially, No. 30T-30 and No. 30T-36 respectively shown in FIGS. 12 and13 are effective bit patterns which fulfill the above conditions well.

Namely, in the case of the bit pattern of No. 30T-30, a mark and a spaceas long as 8T are provided. Therefore, the amplitude control can beperformed stably and at high speed. In addition, short marks/spaces andlong marks/spaces are provided substantially uniformly. Therefore, thePLL locking and the adaptive equalization locking can be performedstably and at high speed.

In the case of the bit pattern of No. 30T-36, 5T, at which the maximumamplitude is obtained, is included. Therefore, the amplitude control canbe performed at higher respondability.

According to these bit pattern, high-speed and stable amplitude control,PLL locking and adaptive equalization locking can be easily realizedwhen the recording data at the start of a zone, immediately before whichno data is recorded, is reproduced. For example, it is not necessary torecord dummy data for locking at the start of the recording data, and sosuch a loss in the recording capacity can be avoided.

By the bit pattern of No. 30T-36, the maximum amplitude is obtained at ahigh frequency. Therefore, the envelope of the reproduction signal canbe detected easily. It is not incorrectly determined whether data isrecorded or not recorded in a block of interest. This makes it possibleto put the operation of amplitude control, PLL locking and adaptiveequalization locking on hold in an unrecorded zone and to start theoperations immediately at the start of the data-recorded zone. Forreproducing the recording data at the start of a zone, immediatelybefore which no data is recorded, a sufficient zone for locking controlcan be obtained.

In the above-described embodiment, the bit patterns shown in FIGS. 10through 13 include bit lengths in the order from a shorter length to alonger length. The order is not limited to this, and may be different.

In the above-described embodiment, the bit patterns having a length of20T, 22T or 30T are provided. The present invention is not limited tothese. Substantially the same effect is provided as long as the bitpattern has a length which is a divisor of the length of the run-inarea.

Embodiment 6

In this embodiment, an existing BD and an optical disc having a higherrecording density than that of the BD (hereinafter, referred to as a“high density disc”) will be described.

FIG. 14(A) shows an example of a BD having a conventional recordingdensity. In this embodiment, the term “conventional recording density”means 25 GB per information recording layer.

In the BD, the laser light wavelength of an optical beam 123 is 405 nm,the numerical aperture (NA) of an objective lens 220 is 0.85, and thelength of a recording mark 121 which is shortest (2T) among variouslengths of marks 120 on the track 2 is 149 nm.

FIG. 14(B) shows an example of a high density disc. In the high densitydisc, the recording density is assumed to be 33.4 GB per informationrecording layer, namely, 1.336 times of the conventional recordingdensity.

Like in the case of the BD, in the high density disc, the laser lightwavelength of the optical beam 123 is 405 nm and the numerical aperture(NA) of the objective lens 220 is 0.85. The length of a recording mark125 which is shortest (2T) among various lengths of marks 124 on thetrack 2 is 111.5 nm, which is shorter than the shortest recording mark121 of the BD. Owing to this, a higher recording density than that ofthe BD is realized.

Now, the OTF cutoff frequency of the BD and the high density disc willbe described.

Where the three parameters, i.e., the laser light wavelength λ (405 nm±5nm, i.e., 400 through 410 nm), the numerical aperture NA (0.85±0.01,i.e., 0.84 through 0.86), and the length P of the shortest mark+theshortest space (in the case of 17 modulation, P=2T+2T=4T) are used, whenthe reference T decreases to fulfill P<λ/2NA, the OTF cutoff frequencyis exceeded.

The reference T corresponding to the OTF cutoff frequency when NA=0.85and λ=405 is:

T=405/(2×0.85)/4=59.558 nm.

With the laser light wavelength and the numerical aperture which are thesame as those of the BD, the recording capacity at which the spatialfrequency of the shortest recording mark exceeds the OTF cutofffrequency is about 31 GB. The recording capacity of the BD is smallerthan this value, and so the OTF cutoff frequency is not exceeded. Bycontrast, the recording capacity of the high density disc shown in FIG.14(B) exceeds this value, and so the OTF cutoff frequency is exceeded.Thus, it is understood that the data structure of the run-in areaaccording to the present invention described so far is very useful forthe high density disc.

FIG. 15 shows a format of a block 153 of the BD.

The block of the BD includes a run-in area, a data area, a run-out areaand a guard area in this order.

The run-in area is located immediately before the data area, and aprescribed bit pattern is recorded therein. The run-in area has a lengthof 2760T.

In the BD, user data as a recording target is divided by in units of 64kB, and a modulation signal obtained by performing prescribed errorcorrection coding processing and modulation processing (1-7 modulation)on each divided unit is generated. In the data area, marks correspondingto such a modulation signal are recorded. The data area has a length of958272T.

The run-out area is located immediately after the data area, and aprescribed bit pattern is recorded therein. The run-out area has alength of 1104T.

The guard area is not added to any block in the middle of a series ofblocks which are being continuously recorded. The guard area is locatedimmediately after the run-out area of the block located at the end ofthe recording, and a prescribed bit pattern is recorded therein. Theguard area has a length of 540T.

FIG. 16 shows the patterns of the run-out area and the guard area of theblock 153 in detail.

The run-out area includes an end SYNC area, an end indicator area, and arepeat pattern area.

In the end SYNC area, a 30T-long SYNC pattern is recorded like in thedata area. The SYNC pattern has a length of 30T.

The end indicator area indicates that the data area is terminated. Inthe end indicator area, 9T is recorded six times in repetition, and theend indicator area has a length of 54T.

In the repeat pattern area, the same repeat pattern as that in therun-in area is recorded. The repeat pattern area has a length of 1020T.

The guard area includes a repeat pattern area and a power control area.

In the repeat pattern area, the same repeat pattern as that in therun-in area is recorded so as to be continued from the end of the repeatpattern of the immediately previous run-out area. The repeat patternarea has a length of about 220T.

The power control area is usable for power control performed at the timeof termination of recording. The pattern to be recorded in the powercontrol is not specifically defined. The power control area has a lengthof about 320T.

As described above, the same repeat pattern as that in the run-in areais recorded both in the run-out area and the guard area. Accordingly,for example, where the repeat patterns of the run-in area shown in FIG.6 are adopted, the run-in area, the run-out area and the guard area canbe each identified with certainty.

In the above-described embodiments, the shortest bit length is 2T, andthe spatial frequency of 2T exceeds the OTF cutoff frequency because ofan increase of the recording density. The reproduced waveform and thelike in such a case are provided. The present invention is not limitedto these.

In the above-described embodiments, an example in which the spatialfrequency of only 2T exceeds the OTF cutoff frequency is provided. Thepresent invention is also effective to an optical disc in which thespatial frequency of a plurality of bit lengths including the shortestbit length exceeds the OTF cutoff frequency. In such a case, a patternincluding bit lengths corresponding to a spatial frequency not exceedingthe OTF cutoff frequency may be used as the run-in bit pattern used forthe run-in area.

In the above-described embodiments, a recordable optical disc and anoptical disc apparatus for such an optical disc are explained as anexample. Substantially the same effects are provided for areproduction-only optical disc and an optical disc apparatus for such anoptical disc.

The elements of the optical disc apparatus according to the presentinvention can be implemented as an LSI, which is an integrated circuit.The elements of the optical disc apparatus may be individually formed asa one-chip device, or a part or the entirety thereof may be incorporatedinto a one-chip device.

Here, the integrated circuit is referred to as an LSI. The integratedcircuit may be referred to as an IC, LSI, super LSI, or ultra LSIdepending on the degree of integration.

The integrated circuit of the present invention is not limited to anLSI, and may be implemented as a dedicated circuit or a general purposeprocessor. An FPGA (Field Programmable Gate Array) which is programmableafter the production of an LSI or a reconfigurable processor in whichthe circuit cell connection or setting in the LSI is reconfigurable maybe used.

When another circuit integration technology replacing the LSI appears bythe development of the semiconductor technologies or by derivation fromthe semiconductor technologies, such a technology may be used tointegrate the functional blocks. Application of biotechnology or thelike is one possibility.

Finally, a brief supplemental explanation will be given regarding a BD(Blu-ray disc) as an example of optical disc according to the presentinvention. The main optical constants and physical formats of a Blu-raydisc are disclosed in “Blu-ray Disc Dokuhon” (Blu-ray Handbook)published by Ohmsha, Ltd. or the white papers put on the web site of theBlu-ray Association (http://www.blu-raydisc.com/).

For the BD, laser light having a wavelength of 405 nm (where thetolerable error range is ±5 nm, 400 to 410 nm) and an objective lenshaving NA=0.85 (where the tolerable error range is ±0.01, 0.84 to 0.86)are used. The track pitch is 0.32 μm. The channel clock frequency is 66MHz (66.000 Mbits/s) at the BD standard transfer rate (1×), 264 MHz(264.000 Mbits/s) at the BD4× transfer rate, 396 MHz (396.000 Mbits/s)at the BD6× transfer rate, and 528 MHz (528.000 Mbits/s) at the BD8×transfer rate. The standard linear velocity (reference linear velocity,1×) is 4.917 m/sec.

The thickness of a protective layer (cover layer) is decreased asfollows as the numerical aperture is increased and so the focal distanceis shortened. The thickness of the protective layer is also decreased inorder to suppress the influence of a spot distortion caused by a tilt.In contrast to 0.6 mm in the case of a DVD, the thickness of theprotective layer of a BD may be 10 to 200 μm among the total thicknessof the medium of about 1.2 mm (more specifically, where the substratehas a thickness of about 1.1 mm, a transparent protective layer having athickness of about 0.1 mm is provided in a single layer disc, and aprotective layer having a thickness of about 0.075 mm and a spacer layerhaving a thickness of about 0.025 mm are provided in a two layer disc).In a disc including three or more layers, the thickness of theprotective layer and/or the spacer layer is further decreased.

In order to protect such a thin protective layer against being damaged,a projection may be provided outside or inside a clamp area. Especiallywhere the projection is provided inside the clamp area, the followingadvantages are provided in addition to protecting the protective layeragainst being damaged. Since the projection is close to the central holeof the disc, the load on the rotation spindle (motor), which would beotherwise caused due to the weight balance of the projection, can bealleviated, and the collision of the projection and the optical head canbe avoided because the optical head accesses the information recordingarea outside the clamp area.

Where the projection is provided inside the claim area, the specificposition of the projection may be as follows, for example, in a dischaving an outer diameter of 120 mm. Where the central hole has adiameter of 15 mm and the clamp area is provided in a region from adiameter of 23 mm to a diameter of 33 mm, the projection is providedbetween the central hole and the clamp area, namely, in a region from adiameter of 15 mm to a diameter of 23 mm. In this case, the projectionmay be provided at a position a certain distance away from the centralhole (for example, the projection may be separated from the edge of thecentral hole by equal to or more than 0.1 mm (or/and equal to or lessthan 0.125 mm)). Alternatively, the projection may be provided at aposition a certain distance away from the clamp area (for example, theprojection may be separated from the inner end of the clamp area byequal to or more than 0.1 mm (or/and equal to or less than 0.2 mm)).Still alternatively, the projection may be provided at a position acertain distance away both from the edge of the central hole and theinner end of the clamp area (specifically, the projection may beprovided in a region from a diameter of 17.5 mm to a diameter of 21.0mm). The height of the projection may be determined such that theprotective layer is unlikely to be damaged or the disc is easily raisedin terms of balance. If the projection is excessively high, anotherproblem may arise. Hence, for example, the height of the projection maybe equal to or less than 0.12 mm from the clamp area.

The stacking structure of the layers may be as follows. In the case of,for example, a one-sided disc used for information reproduction and/orrecording with laser light incident on the side of the protective layer,where there are two or more recording layers, there are a plurality ofrecording layers between the substrate and the protective layer. Themulti-layer structure in such a case may be as follows, for example. Areference layer (L0 layer) is provided at the position which is farthestfrom the light incidence surface and is away from the light incidencesurface by a prescribed distance. Other layers (L1, L2, . . . Ln) arestacked on the reference layer toward the light incidence surface whilethe distance from the light incidence surface to the reference layer iskept the same as the distance from the light incidence surface to therecording layer in a single-layer disc (for example, about 0.1 mm). Bykeeping the distance to the farthest layer the same regardless of thenumber of layers in this manner, the following effects are provided. Thecompatibility can be maintained regarding the access to the referencelayer. In addition, although the farthest layer is most influenced bythe tilt, the influence of the tilt on the farthest layer is preventedfrom being increased as the number of layers increases. The reason isthat the distance to the farthest layer is not increased even if thenumber of layers increases.

Regarding the spot advancing direction/reproduction direction, eitherthe parallel path or the opposite path is usable, for example. By theparallel path, the spot advancing direction/reproduction direction isthe same in all the layers, namely, is from the innermost end toward theoutermost end in all the layers, or from the outermost end toward theinnermost end in all the layers. By the opposite path, where the spotadvancing direction/reproduction direction is from the innermost endtoward the outermost end in the reference layer (L0), the spot advancingdirection/reproduction direction is from the outermost end toward theinnermost end in L1 and is from the innermost end toward the outermostend in L2. Namely, the reproduction direction is from the innermost endtoward the outermost end in Lm (m is 0 or an even number) and is fromthe outermost end toward the innermost end in Lm+1 (or is from theoutermost end toward the innermost end in Lm (m is 0 or an even number)and is from the innermost end toward the outermost end in Lm+1). In thismanner, the reproduction direction may be opposite between adjacentlayers.

Now, the modulation system of the recording signal will be brieflydescribed. For recording data (original source data/pre-modulationbinary data) on a recording medium, the data is divided into parts of aprescribed size, and the data divided into parts of the prescribed sizeis further divided into frames of a prescribed length. For each frame, aprescribed sync. code/synchronization code stream is inserted (framesync. area). The data divided into the frames is recorded as a data codestream modulated in accordance with a prescribed modulation rulematching the recording/reproduction signal characteristic of therecording medium (frame data area).

The modulation rule may be, for example, an RLL (Run Length Limited)coding system by which the mark length is limited. The notation“RLL(d,k)” means that the number of 0's appearing between 1 and 1 is dat the minimum and k at the maximum (d and k are natural numbersfulfilling d<k). For example, when d=1 and k=7, where T is the referencecycle of modulation, the length of the mark or space is 2T at theshortest and 8T at the longest. Alternatively, the modulation rule maybe 1-7PP modulation, in which the following features [1] and [2] areadded to the RLL(1,7) modulation. “PP” of 1-7PP is an abbreviation ofParity preserve/Prohibit Repeated Minimum Transition Length.

[1] “Parity preserve” represented by the first “P” means that whetherthe number of 1's of the pre-modulation source data bits is an oddnumber or an even number (i.e., Parity) matches whether the number of1's of the corresponding post-modulation bit pattern is an odd number oran even number.[2] “Prohibit Repeated Minimum Transition Length” represented by thesecond “P” means a mechanism for limiting the number of times theshortest marks and spaces are repeated on the post-modulation recordingwave (specifically, a mechanism for limiting the number of times 2T isrepeated to 6).

Here, an area including the synchronization code stream and the datacode stream is referred to as a “frame area”, and a unit including aplurality of (e.g., 31) frame areas is referred to as an “address unit”.In an address unit, an inter-code distance between a synchronizationcode stream included in an arbitrary frame area of the address unit anda synchronization code stream included in a frame area other than thearbitrary frame area may be 2 or greater. The “inter-code distance”means the number of bits which are different between two code streams.Owing to the arrangement in which the inter-code distance is 2 orgreater, even if a 1-bit shift error occurs in one of the streams to beread due to an influence of noise or the like during reproduction, sucha stream is not identified as the other stream by mistake.Alternatively, the inter-code distance between a synchronization codestream included in a frame area located at the start of the address unitand a synchronization code stream included in a frame area located at aposition other than the start of the address unit may be 2 or greater.Owing to such an arrangement, it is easily distinguished whether thesynchronization code stream is at the start or not, or whether thesynchronization code stream is at the junction of address units or not.

The term “inter-code distance” encompasses an inter-code distance in anNRZ notation of the code stream in the case of NRZ recording and also aninter-code distance in an NRZI notation of the code stream in the caseof NRZI recording. Therefore, in the case of recording performed by theRLL modulation, “RLL” means that the number of continuous high-level orlow-level signals on the recording wave of NRZI is limited and so meansthat the inter-code distance is 2 or greater in the NRZI notation.

Now, the recording system will be described. By forming a groove in amedium, groove parts and inter-groove parts between groove parts areformed. There are various recording systems; namely, data may berecorded in the groove parts, in the inter-groove parts, or both in thegroove parts and the inter-groove parts. A system of recording on aconvex side as seen from the light incidence surface, among the grooveparts and the inter-groove parts, is called “on-groove system”, whereasa system of recording on a concave side as seen from the light incidencesurface is called “in-groove system”. According to the presentinvention, it is not specifically limited whether the on-groove systemis used, the in-groove system is used, or a system of permitting eitherone of the two systems is used.

In the case of using the system of permitting either one of the twosystems, recording system identification information which indicateswhether the on-groove system or the in-groove system is used may berecorded on the medium, so that the recording system of the medium, theon-groove system or the in-groove system, can be easily identified. Fora multi-layer medium, recording system identification information oneach layer may be recorded. In such a case, recording systemidentification information on all the layers may be recorded on areference layer (the layer farthest from the light incidence surface(L0), the layer closest to the light incidence surface, the layer towhich the optical head is determined to access first after the opticaldisc apparatus is started, etc.). Alternatively, recording systemidentification information on each layer may be recorded on therespective layer, or recording system identification information on allthe layers may be recorded on each layer.

The areas in which the recording system identification information canbe recorded include a BCA (Burst Cutting area), a disc information area(an area which is inner or/and outer to the data recording area andmainly stores control information; in the reproduction-only area, suchan area may have a track pitch larger than that of the data recordingarea), a wobble (recorded in superimposition on the wobble), and thelike. The recording system identification information may be recorded inany one of these areas, a plurality of areas among these areas, or allof these areas.

The wobble start direction may be opposite between the on-groove systemand the in-groove system. Namely, where the wobble start direction inthe on-groove system is from the innermost end toward the outermost endof the disc, the wobble start direction in the in-groove system may befrom the outermost end of the disc (alternatively, where the wobblestart direction in the on-groove system is from the outermost end of thedisc, the wobble start direction in the in-groove system may be from theinnermost end of the disc). By setting the wobble start direction to beopposite between the on-groove system and the in-groove system in thismanner, the tracking polarity can be the same whichever system, theon-groove system or the in-groove system, may be used. The reason is asfollows. In the on-groove system, the recording is made on the convexside as seen from the light incidence side, whereas in the in-groovesystem, the recording is made on the concave side as seen from the lightincidence side. Therefore, if the groove depth is the same in thesesystems, the tracking polarity is opposite. By setting the wobble startdirection to be opposite between the two systems, the tracking polaritycan be made the same.

A recording film can have the following two recording characteristicsbecause of the relationship between the reflectance of the recorded partand the reflectance of the unrecorded part. They are HtoL characteristicat which the reflectance of the unrecorded part is higher than thereflectance of the recorded part (High-to-Low), and LtoH characteristicat which the reflectance of the unrecorded part is lower than thereflectance of the recorded part (Low-to-High). According to the presentinvention, it is not specifically limited whether the HtoLcharacteristic is used, the LtoH characteristic is used, or either oneof the two is permissible as the characteristic of the recording film ofthe medium.

In the case where either one of the two is permissible, recording filmcharacteristic identification information which indicates whether therecording film has the HtoL characteristic or the LtoH characteristicmay be recorded on the medium, so that it can be easily identified whichcharacteristic the recording film has. For a multi-layer medium,recording film characteristic identification information on each layermay be recorded. In such a case, recording film characteristicidentification information on all the layers may be recorded on areference layer (the layer farthest from the light incidence surface(L0), the layer closest to the light incidence surface, the layer towhich the optical head is determined to access first after the opticaldisc apparatus is started, etc.). Alternatively, recording filmcharacteristic identification information on each layer may be recordedon the respective layer, or recording film characteristic identificationinformation on all the layers may be recorded on each layer.

The areas in which the recording film characteristic identificationinformation can be recorded include a BCA (Burst Cutting area), a discinformation area (an area which is inner or/and outer to the datarecording area and mainly stores control information; in thereproduction-only area, such an area may have a track pitch larger thanthat of the data recording area), a wobble (recorded in superimpositionon the wobble), and the like. The recording film characteristicidentification information may be recorded in any one of these areas, aplurality of areas among these areas, or all of these areas.

The present invention is usable for an increased recording density of anoptical disc and so is useful, and can be utilized for large capacityoptical discs, and optical disc reproducing apparatuses, optical discrecording apparatuses, optical disc reproducing methods, optical discrecording methods, and integrated circuits usable for such opticaldiscs.

1. An optical disc, comprising tracks, each divided into a plurality ofrecording blocks; wherein: each of the plurality of blocks includes arun-in area and a data area; in the run-in area, a prescribed run-in bitpattern is recordable; in the data area, bit patterns having a pluralityof bit lengths obtained by modulating data as a recording target inaccordance with a prescribed modulation rule are recordable; where theshortest mark among the bit patterns having the plurality of bit lengthshas a length of TM nm, the shortest space among the bit patterns havingthe plurality of bit lengths has a length of TS nm, laser light used forirradiating the track has a wavelength of 2 nm, and an objective lensfor collecting the laser light has a numerical aperture NA,TM+TS<λ/(2×NA) is fulfilled; and the run-in bit pattern recordable inthe run-in area includes the bit patterns having the plurality of bitlengths, from which a bit pattern having a bit length equal to orshorter than λ/(2×NA)/2 has been excluded.
 2. A reproducing method forreproducing data recorded on the optical disc of claim 1, thereproducing method comprising the steps of: detecting a reproductionsignal from the track of the optical disc; extracting a channel clockthat is synchronized to the reproduction signal in the run-in area andkeeping on the synchronization in the data area, extracting a digitalsignal by sampling the reproduction signal using the channel clock; anddemodulating data from the digital signal.
 3. A recording method forrecording data on the optical disc of claim 1, the recording methodcomprising the steps of: generating the run-in bit pattern; generating adata bit pattern by modulating the data in accordance with a prescribedmodulation rule; and in each of the plurality of blocks, recording therun-in bit pattern in the run-in area and recording the data bit patternin the data area.